code: def _dft_matrix(dft_length):
      """Calculate the full DFT matrix in numpy."""
      omega = (0 + 1j) * 2.0 * np.pi / float(dft_length)
      # Don't include 1/sqrt(N) scaling, tf.signal.rfft doesn't apply it.
      return np.exp(
          omega * np.outer(np.arange(dft_length), np.arange(dft_length))
      )
  
file_path: magenta/magenta/models/onsets_frames_transcription/melspec_input.py
imports: import math
  from magenta.models.onsets_frames_transcription import mfcc_mel
  import numpy
  import tensorflow.compat.v1
label_desc: Use image node_id 2 for calling a global function with example usage: _dft_matrix(dft_length) and returns: np